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Blood drop size in passive dripping from weapons
N Kabaliuk1, M C Jermy, K Morison
1Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand.
Forensic Science International
|April 20, 2013
Summary
This study measured blood droplet sizes from various objects, finding that sharper objects produce smaller drops. Understanding droplet size is crucial for analyzing bloodstain patterns at crime scenes.
Area of Science:
- Forensic Science
- Fluid Dynamics
Background:
- Passive dripping creates bloodstains at crime scenes, forming drip trails.
- Previous research links stain size, satellite stains, surface roughness, droplet size, and fall height under ideal conditions.
Purpose of the Study:
- To measure blood droplet sizes from objects simulating hand-held weapons.
- To provide data for inferring fall height from bloodstain patterns.
Main Methods:
- Pig blood and distilled water were used, with blood properties controlled.
- Drips were formed from stainless steel objects (cylinders, plates, knife, wrench) of varying roughness.
- High-speed imaging captured falling droplet characteristics.
Main Results:
- Primary blood droplet size ranged from 4.15±0.11 mm to 6.15±0.15 mm, with smaller sizes from sharper objects.
- Droplet size showed weak correlation with surface roughness.
- Accompanying droplet count increased with object size, but not significantly with surface texture.
Conclusions:
- Blood droplets from passive dripping are influenced by object shape and size.
- Findings contribute to more accurate interpretation of bloodstain evidence in forensic investigations.
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